Showing papers by "S. Michael Kilbey published in 2005"

Kinetics of surface-initiated photoiniferter-mediated photopolymerization

Abstract: Surface-tethered poly(methyl methacrylate) films were synthesized by surface-initiated photoiniferter-mediated photopolymerization (SI-PMP), and the kinetics of film growth were followed by measuring layer thickness as a function of reaction time, monomer concentration, and light intensity using variable angle ellipsometry. The initial rate of photopolymerization had approximate first-order dependence on monomer concentration. However, the rate of photopolymerization decreased with reaction time, indicating the presence of termination reactions. To determine which termination reactions are prevalent, kinetic models accounting for bimolecular termination as well as chain transfer to monomer were developed for the photoiniferter-mediated photopolymerization reactions and used to analyze the experimental data. Comparisons of model predictions to experimental data as functions of reaction time and light intensity suggest that bimolecular termination is the dominant termination mechanism in these systems for t...

Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Abstract: Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator-functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled. Formation of polystyrene brushes at T < Tg by ATRP of styrene from α-bromoester initiator-functionalized poly(glycidyl methacrylate) layers.

Inkjet-printed monolayers as platforms for tethered polymers.

Abstract: Combining inkjet printing and atom-transfer radical polymerization (ATRP) provides a straightforward and versatile method for producing patterned polymer surfaces that may serve as platforms for a variety of applications. We report the use of drop-on-demand technology to print binary chemical gradients and simple patterns onto solid substrates and, by using surface-confined ATRP, amplify these patterns and gradients. Chemically graded monolayers prepared by inkjet printing dodecanethiol and backfilling with 11-mercaptoundecanol showed continuous changes in the water contact angle along the gradient. These samples also exhibited a distinct change in the intensity of methyl group and C-O stretching modes along the gradient. Graded or patterned polymer layers were produced by growing, with ATRP, tethered poly(methyl methacrylate) (PMMA) layers from gradient or patterned printed monolayers that contained a bromo-capped initiator. Atomic force microscopy and optical microscopy confirmed that the PMMA layers amplified the underlying printed initiator layer with remarkable fidelity.

MALDI-TOF MS Characterization of Carboxyl-End-Capped Polystyrenes Synthesized Using Anionic Polymerization

Abstract: A comparative study of three strategies used to synthesize well-defined carboxyl-end-capped polystyrenes is reported. Structural characterization was carried out using a combination of thin-layer chromatography (TLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). For the reaction of polystyryl anions with 4-bromo-1,1,1-trimethoxybutane, in addition to the major product, Bu−PS−CH2CH2CH2COOH, four byproducts were observed. Their mass values suggest the following structures: Bu−PS−H, Bu−PS−CH3, Bu−PS−CH2CHCH−CHO, and Bu−PS−CH2CH2CH2−CO−PS−Bu. The reaction of polystyryl anions with succinic anhydride generated the targeted compound, Bu−PS−CO−CH2CH2COOH, but also yielded the byproducts Bu−PS−H and dimer Bu−PS−CO−CH2CH2−CO−PS−Bu. Under appropriate conditions, the reaction of carbon dioxide gas with polystyryl anions could yield quantitative carboxyl chain-end-functionalization.